Your Arcam cannot read the SACD layer of the discs you mention, but they are hybrid discs, with a CD layer as well as an SACD layer--you're hearing the CD layer. I think the big difference between the old and new redbook discs is that the new Dylan discs were remastered much better than before. I didn't know that the Dylan CD layer was HDCD encoded, but there are apparently a number of such discs that are HDCD but not labeled as such, so maybe this was one of them. HDCD is still alive (Reference Recordings is its biggest proponent, but other labels use it too), just hadn't heard of Sony using it till now!